NUCLEIC ACID RELATED COMPOUNDS .73. FLUORINATION OF URIDINE 2'-THIOETHERS WITH XENON DIFLUORIDE OR (DIETHYLAMINO)SULFUR TRIFLUORIDE - SYNTHESIS OF STABLE 2'-[ALKYLSULFONYL]-2'-DEOXY-2'-FLUOROURIDINES OR 2'-[ARYLSULFONYL]-2'-DEOXY-2'-FLUOROURIDINES

Treatment of 2,2'-anhydro-1-beta-D-arabinofuranosyluracil with thiolate anions gave the 2'-S-alkyl(and aryl)-2'-thiouridines (1). Oxidation of 3',5'-di-O-acetyl-2'-S-alkyl(and aryl)-2'-thiouridines (2) with 3-chloroperoxybenzoic acid (MCPBA) gave the diastereomeric sulfoxides 4. Treatment of 2 with XeF2 or 4 with (diethylamino)sulfur trifluoride/SbCl3 gave the diastereomeric 3',5'-di-O-acetyl-2'-S-alkyl(and aryl)-2'-fluoro-2'-thiouridines (9). These alpha-fluoro thioethers were oxidized (MCPBA) to their stable sulfone derivatives 11 that are analogues of the biologically active 2'-deoxy-2',2'-difluoro nucleosides. Stereochemistry (2'S) and conformations of the major diastereomers were established by X-ray crystallography. Efficient conversions of 11 to the cytidine alpha-fluoro sulfones 14 were achieved.